The noise checks at Goodwood are quite strict, and I have seen a couple of MTWs rejected and unable to participate.
Last time (2021?) one MTW was running with additional "cans" on the end of the pipes, I think he mentioned they were originally designed for a TVR?
I may be wrong but I think they ask drivers to rev to 75% of max revs. However they do not seem to check this on the rev counter and take your word for it.
I am sure some of those at last years event will be along soon to give you a more definitive answer.